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March 13, 1945. N. D. PRESTON CODED TRACK CIRCUIT SIGNALING SYSTEM Original Filed Nov. 9, 1940,

Snnentor Patented Mar. 13, 1 945 'pobnn CK CIR01 "J1 "T SIGNALING W YST Neil 11). Preston, Rbchester, ,N. Y., assignor to General Railwayfiignal :Gonfiiany, Rochester,

Ifhis inverition relates to cqddtfafik feiriiiiits *mteyni ttently 'conne'dteat thej tr'ackt rails bye l'tiotle transmitter re'lay '"oji'j equivalent means; and [it a."'s.tra;y-*currnt of the py'operpqlarity and intensity to "operette this trak felaythqiild exis't, [then this "'trer kfrel'ay is intermittently energized, jre ardress o the =e'xi'slttnce of the 'inyerse'jgode "tentlycbnneetedtd the sustained"potentia1 aeross the ttejkfe ilsptn dfthu picks up and drops as the transmitter relay operates) suh false selfabove mentioned, 1357 renderin the tran nfltter "relay ineffective while t TY-cede track frl'ay is energized, so tfiaitjwhenfa 'strjay turfeptexists 1 trers iti en 50f this transmitter relay "is j'fMtOlfl'fimany ttdppeaj gmd no longer 'acts te- "connect tettm against improper operation by "strayturgrente'is til-gt the o'fi-cod'e p111$e must easefgnd the bit-node 'track relay rl'easefibefore the tramsmitter rel'ay'may be energized for thegnextdr iven thigher eb de rates, as;we1 1'afsth lower bo demtes; Tis desirame to, "employ fa relatively thtrtoijtone pulse. when the duration of the off-code of}; track 't'elay at uniftrm finteryals hdwever, is desirdbfre fnr more efficient and uniform contrbl bf thel fle-ctidih'g means, particularly the type usinglt'm "imputse tie-ceding transformen,

"iii wew of these 'cofi idemtions; it is propbeeti accordance with this invention totpro'vide means ferv attifici'ally 'jpro'l'on'gin'g the operation mode retponsivejmeens. t

Geirfex ell'ly-"spealdhg, 25nd withtut attemptmgiro track =re1ay "aha. the cbling centadt's'previdin' the fitiven "code pulses ineuche'way-that 'this repeater relay; atter each operationther'edf in respbnse to the eheig'i'za'tien o'f the'tr'ack feley; 're'rnains in sueh Operated condition, independently o f the deenergization o'f saiii track rerajy upon cessapulse. in tmsway, Whilefthe qff-cdde tmtktelay fellows the inverse "cede-pulses and may be uslefi -'t0 provide the desired stray curfefit, the repeater track "relay is enel' *gizeii' ant fita'eheTizii stitstantially equal intei'val's' in corres ondence with the driven code 20 t t in one embodiment bf the mvention, th s re;-

tybe a-n'i was its armature 6r c'entadt element op- "erfate'di beek anfi forth in response to the 'nergiization of the trak'r'elay and t1bs1'1rett the cenin-g contacts respectivel In another embodi- {Fig -2 illustrates another embcsd-iment ment of the invention, the repeater relay is 'a neutrzkl "relay maintained e'nefgized after each "eneigizaition "thereof in r'eS'pon'se to the Operation of the track relay *by a *s'titik circuit epene'd' uifion -'cl'osui'e of the code contacts to provide the next. fi'riven coiie pulse.

'varieus dthe'r cha'natteri'stic features and attributes -of the inve'rit'ion will be in p'art apparent "and in part pointei out as the aescriptidn to- The aocempany-ing drawing illustrates in a 's'ir'nplffiefl and diagrammatic malnn'erj'cer'ta-in "specific emba'diments 0f the inventitn, the nature of the illustration being intended to facilitate. ah understanding 0'; the structural organization "and mode or dperdtion of the i'n'ventidn, .iather than te show the pafticular arrangement and detailed tonstmctibn 'o'f theiehi'ts' p rfeTabIYempi-eyed in practice. In the diaWihg-- t t S'Fig. 1 illustrates a t pical organization fof pro-- v idiri'g inverse or o fi-cod'e impulses for a track section, together with 'one embodiment of the invention {for providing utfi fo-rm relay operation for the control "of '"cbde 'rewdnsiv'e means: and

of the invention forthe same pur tse. 1

It is assumed that'th'e coded track c'ircuitvv'iu Me at "the eonvehtiona lfiirect eurrenttyp and that the signal gontroning 'Or driven edde's at the arrow, will be employed for governing the indi,-" cations of a way-side signal I at the entrance to such track section, and that the inverse or offcode pulses in the opposite direction, as indicated by the dotted arrow, will be employed to govern the energization of a relay OCH to provide approach lighting for some other signal not shown, control of approach locking fora power operated track switch, or for some like purpose. The selection of the code rates to be efiective at any given time for governing the indications of signal I may be determined in any suitable manner, and the relay X is typical or illustrative of means suitable for this purpose. Also, as illustrated in Fig. 1, it is assumed that the inverse or off-code will be controlled by the presence of a train in one or more adjoining track sections, due to theoccupancy of some other coded track circuit or the like; and the relay Y is typical or illustrative of such a means for cutting off the inverse code prior to and independently of the entrance of a train into the track section shown.

tion shown in Fig. 1, a transmitter relay CP is intermittently energized by the closure of coding contactsClBll or 015 as selected by the contact 9 of the relay X; and this transmitter relay CP.

operates a contact finger 4 to connect alternately across the track rails 2 of the track section shown, a track battery 5 in series with a suitable limiting resistance 6, and'an oil-code track relay OCTR,

as said transmitter relay CP is energizedand-deenergized respectively; The off-code track relay OCTR, is preferably of the two-position biased polar type, and operates a contact finger from the biased position shown by a solid linetothe other'operated position shown. by a dotted line; when this relay is energized by an inverse code pulse.

A significant characteristic of this invention is that the-energizing circuit for the transmitter relay CP includes the contact finger of the track. relay OCTR in the deenergized biased position,

front or back contacts 9 of relay X, as the case maybe, through the transmitter relay GP, to

The equipment at the other end of the track section for de-coding the driven codes and transmitting inverse code pulses may be of any suitable form in accordance with regular practice. In the arrangement illustrated in Fig. 1, an impulse .relay IMP'of the two-position biased polar type is arranged to act, when it is deenergized and its contact finger I0 is moved to the biased or-lefthand solid line position, to connect a code following track relay CF'I'R across the track rails 2.,

When the relay IMP is energized as presently explained, and its contact finger In is-moved to the right-hand or dotted position, a suitable battery H is connected across the track rails to provide the desired inverse or off-code pulse, the ener- Considering-the particular form of the invengization of the relay IMP being of limited duration so that this inverse code pulse is relatively short.

The code following track relay CF'IR operates suitable de-coding means for governing the indications of signal-l in the usual manner. As illus trated, the contact fingerLIZ of the'relay CFIR energizes alternately the two halves of the prirmary of a de-coding transformer l3 having the usual mid-tap connection. One secondary of this transformer I 3 is connected through rectifying contacts M on the relay CF'IR to the home relay JH; Another secondary of the de-coding transformer l3 energizes a circuit including a condenser 29 and tuned for the 180 code rate for impulsing the primaryof a transformer l6 having .its secondary connected through a full-wave rectifier I! to a distant relay ID. The home relay IH and the distant relay ID govern the green, yellow and red indications of the signal I in the usual manner.

Consideringthe arrangement shown for providing inverse code pulses, an impulse winding [8 onthe de-coding transformer I3 acts to energize temporarily the impulse relay IMP when the code following track relay CFTR is deenergized at the end of each on period of the .driven code. This impulse winding I8 is so wound and connected to the relay IMP that the momentary voltage induced in said winding when the relay CFTR drops sends current through the relay IMP ina direction to move its contact finger 10 from the biased position, whilethe voltage inducedin theimpulse windinglB when the relay 'CFIR picks up is in a direction to hold the relay IMP in itsbiased position. If as assumed the inverse code is to be controlledby occupancy ofone or more track sections in the rear, thecircuit'for the impulse. relay IMP includes. a 'Irontcontatit l9 of the-relay Y exemplifying such control. I I

The inverse code is employed in accordance with this invention to maintain energized suitable code responsive means associated withthetrans- ,mitting or exit end of the .track section,.fa nd, for

satisfactory and efficient operation of such abode responsivemeans, it is desirable to'have contacts operated at substantially uniform intervals.

shorten the "on periods. It is contemplated that quick acting relays will be used, and the system otherwise so organized that the normalinverse code pulses will fit in the normal ofi period'of the driven codes at the highest code rates, with a suitable margin to take care ,of varying ballast resistances and battery voltages, Under the e conditions, ,it can be seen that the period of energization of the foff code track relay OC'I'R{ is likely to be much shorter than the period of' deenergization, particularly at the low code rates. Accordingly, it is desirable to prolong artificially the response to an inverse code to conform with the code rate ineffect, while at thesame time permitting the oil code track relay to follow the code and permit energization of the transmitter relay CP. r f v In the arrangement shown in Fig.1 forthis purpose, a repeater relay TP of the two-position polar magnetic stick type is employed to mainrelay OC'IR by; inverse" codev pulses As illushated, the contact finger Z-U ofrelay TP in its difierent' operated' positions energizes the two halves of a. de-coding transformer 21', the sec;-

. ondary of which, is connected through a rectifying} contact 22 on relay T? to the slow release relay OCH. h

Inthis arrangement of Fig. 1, when the ofi code track relay OCTR: is energized by an inverse code pulse to. move its. contact finger 40 to the netic. stick type, remains in this position, independently ot the deenergization of the track relay OCTR by cessation of the, inverse code pulse and, until. the other winding of this repeater relay T? is energized. When the coding contact Cli8ll or C15, as the case) may be, closesior the next. on period. of. the driven code, and assumthe, track relay OC IR is in the deenergized position, the upper winding of the repeater relay 'I'P is energizedin multiple with. the transmitter relay CP by an obvious circuit, including wire 23, thereby operating the contact fingers and 22 of this repeater relay TP to the other position.

It can. beseen, thatv in, this arrangement, of

Fig. 1 the two-positionjmagnetic stick repeater relay is, operated to one position in response to the reception of an inverse code pulse, and to the other position at the beginning of the next "on period of the driven code pulse, thereby giving a more uniform operation of the contacts of this repeater relay for operation of code responsive means independently of the duration of the inverse code pulses. I

Fig. 2 illustrates a modified organization, in which the coding contacts Cl8fl and C15 are provided with what may .be termed back contacts 24 and 25, which are closed in the left-hand position as shown during the oif intervals of driven code transmission, as well as the regular contacts closed in the right-hand position for energization of the transmitter relay CP. The repeater relay OCTP is a neutral or polar relay having its contacts biased to a deenergized position. The upper winding of thisrelay OCTP is energized by an obvious circuit when the track relay OCTR is energized by inverse code pulse to move its contact 40 to the right-hand position. The lower lower winding of the repeaterr'elayOCTP- isprepared. sothat this repeater relay is held up byits stick circuit until the back contacts of the coding contacts open at the beginning of the next off period. This repeater relayOCTP may operate, contacts 45 and 46' tocontrol the energization of 'a' slow" release relay OCI-Ithrough' a de-coding transformer'z lin the same manner shown and described for" Fig. 1.

It should'be undcrstoodthat' the specific embodiments or the invention shown and described are merely illustrative of the organization and functions characterizing the invention, and that various-adaptations and modifications may be made in the particular constructions and arrangement of parts and circuits illustrated without departing from the invention.

What I claim is: I i I I 1. In a coded track circuit for railroads, a track section, a source of current, an off-code track relay, a transmitter relay forintermittently connecting said source of current and said trackrelay alternately across the track rails of said track winding of the relay OCTP is included in a stick circuit including a front contact 44 of this relay and the back contacts 24 or 25 of the coding contacts Cl8ll and C15 dependent upon the condition of relay X.

Considering the operation of this modification in Fig. 2, assuming relay X energized and the track relay OCTR to be deenergized and the regular coding contacts open as shown, the next time the coding contacts shift the transmitter relay 'CP is energized by a circuit readily traced from through front contact 9 of relay X,

. coding contact C180 in the right-hand position,

relay CP, contact finger 40 of relay OCTR, to This energization of the relay CP causes the application of a driven code pulse in the regular way, and during the next off interval,

the back contact 24 of the coding contacts CIBIJ is closed, and when the repeater relay OCTP is energized in response to the energization of the stick circuit through the front contact 44 and the section at one end, intermittently'operated coding contacts for operating said transmitter relay at a selected code rate, means associated with the other end, of said tracksection for applying code. pulses. of limitedduration during the. off intervals of said driven code, code responsive means including a repeater relay operated, by thev energization of said track, rela by off-code pulses, said code responsive, means also, including control, circuits energized, byoperationof said repeater relay to its difierent conditions, and means for operating said repeater relay from one condition in response to the energization of said track relay and for restoring said repeater relay to said one condition only when said transmitter relay is again operated for the next driven code pulse, whereby the control circuits for said code responsive means are energized by said repeater relay at intervals corresponding substantially with the driven code rate in spite of the relatively short duration of the off-code pulses and energization of said off-code track relay.

2. In a code track circuit for railroads, a track section, a source of current, an off-code track relay, a transmitter relay for intermittently connecting said source of current and said track relay alternately across the track rails of said track i section at one end, intermittently operated coding contacts for closing an energizing circuit for said transmitter relay, said energizing circuit being closed only if said off-code track relay is then deenergized, means associated with the other end of said track section for at times providing offcode pulses for energizing said off-code track relay, a repeater relay operated in response to the energization of saidoff-code track relay and remaining in such operated condition independently of the condition of said track relay until the next operation of said transmitter relay, and code responsive means governed by the operation of said repeater relay.

3. In a coded track circuit for railroads, a track section, a source of current, an off-code track relay, code transmitting means for intermittently track rails during the off interval between the track relay OCTR by an inverse code pulse, the i driven code pulses for the energization of said track relay, a two-position repeater relay of the magnetic stick type, means for operating said repeater relay to one position in response to the energization of said track relay, means for operating said repeater relay to the other position in response to the operation of said code transmitting means, and code responsive means governed by circuits including contacts closed in the different operated positions of said repeater relay.

4. In a coded track circuit for railroads, code transmitting means for alternately connecting a source ofv current and a track relay across the track rails of a track section at one end in accordance with'a selected code rate to provide driven code pulses separated by off intervals, means for providing inverse code pulse at the other end of said track section for the energization of said track relay during said ofi intervals between the driven code pulses, a repeater relay of the magnetic stick type having two windings acting when respectively energized to operate the contact element of that relay to difierent positions, means for energizing one of said windings in response to the energization of said track relay, means for energizing the other of said windings when said code transmitting means is operated, and code responsive means including a slow release relay maintained energized by the continued intermittent operation of the contact element of said repeater relay to its diflerent positions alternately.

5. In a coded track circuit of the character described operating to send inverse code pulses in one direction over the track rails of a track section during the off intervals between driven code pulses over said track rails in the opposite direction, the combination with a track relay responsive to said inverse code pulses, and a transmitter two-position repeater relay of the magnetic stick' type operated to one position by energization of said track relay and to the other position by operation of said transmitter relay, code responsive means governed by circuits including contacts of said repeater relay closed in its diflerent operated positions, and means for preventing operation of said transmitter relay while said track relay is energized.

6. In a code track circuit for railroads, a transmitter relay for alternately connecting a source of current and a track relay across the track rails of a track section at one end, intermittently operated coding contacts, an energizing circuit for said transmitter relay governed by said coding contacts and closed only if said track relay is then deenergized, a repeater relay energized in response to the energization of said track relay, means governed by said coding contacts for maintaining said repeater relay in its energized condition after each operation thereof independently of the condition of said track relay until said coding contacts operate for the next driven code pulse, and code responsive means including a slow release relay maintained energized by the continued intermittent energization and deenergization of said repeater relay.

NEIL D. PRESTON. 

